1. Field of the Invention
The invention relates to methods for encoding and decoding objects with reference to a traffic route network, wherein the encoded information can also be decoded with the aid of databases that differ from a database used for the encoding.
2. Description of Related Art
In traffic telematic applications, in which location-specific data are to be exchanged between a transmitter and a receiver, methods for location referencing—also called location encoding—are needed. Methods are employed that describe the location references for the data to be sent in the database of the transmitter, and methods that evaluate the location references of the transmitted data in the receiver. The evaluation involves interpreting the location references and copying them onto the database of the receiver. The description of the location references must be done such that correct copying of the objects by recognizing the location references in the database of the receiver is possible.
Among others for various applications in traffic telematics (such as TMC, GATS), it is known for a description form for location references (also called location encoding) to be standardized. In these applications, as a rule it is a condition that the described locations be present in both the databases of the transmitter and of the receiver and that they have the same location encoding. In the event of deviations, calibration of the databases is required.
Methods for referencing elements from a digital map are also known, which with respect to location encoding have as a prerequisite only similar databases or digital maps with similar digitization. The description of the location references is done on the basis of geographical location coordinates and other descriptive characteristics. For intersections, as elements of the digital map, certain rules are also defined, which determine the location coordinates and characteristics to be transmitted (German Patent Disclosure DE 197 50 786 A1).
The term “objects” is understood in the present connection to mean information with a geographic reference, including multimedia objects such as video sequences, stationary images, or sounds, and/or elements of a digital map.
With the invention, the intent is that it be possible for already existing objects in the receiver database to be addressed, new objects to be placed in the receiver database, and existing objects to be modified.
Against the background of efforts in search of a universal interface between databases of different map publishers, which naturally applies to partial networks to be transmitted as well, the problem arises of copying the given data sets onto one another, or in other words finding unambiguous associations among the corresponding elements.
However, because of publisher-dictated attribution with regard to both the location coordinates and the “heuristic”, descriptive characteristics, the result is indefiniteness, which makes unambiguous identification of the encoded object difficult.
In general, the construction of databases is oriented to the type of objectively given linkage of its objects. In the case of digital maps, this is a linkage by way of the neighborhood relationships that exist on the basis of direct street connections.
In mathematical terms, what this means is: Since only the intersection of the attributes used in each of the two databases can be used for comparison purposes, the number of characteristics used for the “pair” identification cannot be greater than the number of attributes that the database, with a low density of characteristics, furnishes per object. The extreme case is then the absence of a corresponding object in the comparison database; in that case, the intersection quantity equals zero.